Trigger circuits



July 31, 1951 A. H. dlcKlNsoN TRIGGER CIRCUITS 2 Sheets-Sheet 1 Filed Dec. 29, 1948 July 31, 1951 Filed-Dec. 29, 1948 A. H. DIC KINSON TRIGGER CIRCUITS TEE- @52504/0175 i fig s .All

2 Sheets-Shee 2 'swam' HGENT Patented July 31, 1951 to International Business Machines Corporation, .New York, N. a corporation of New York Application December 29, 194s, semaine. 68,018

3 Claims.

This .invention relates to trigger circuits and more particularly to novel trigger circuits including arrangements for keying inherently binary triggers employing two grid controlled tubes, .each

tubel having its plate coupled t0 a grid of the common source of keying pulses. Each of these arrangements is .disadvantageous in that feedback is applied to the trigger so as to oppose the switching action of the trigger. when high-speed keying of the trigger is attempted, the feedback v.effects predominate and the trigger is thereby rendered non-responsive.

.Another arrangement of the prior art involves connecting the plate resistors ofthe trigger tubes together and to theplate supply voltage through a common resistor. The keying pulses are `applied to the common juncture of-the resistors. arrangement is disadvantageous in that a large keying pulse is required because kof .the low impedance of the common resistor.

Another arrangement involves connecting the grid bias resistors of the tubes together and-t0 a source of bias voltage through a common resistor. The keying pulses are applied to the common juncture of the resistors. This arrange'- ment is disadvantageous in that extremely stable supply voltage is necessary to proper trigger operation as well as careful adjustment of circuit parameters.

Accordingly it is a principal object of the invention to provide a novel circuit arrangement yfor keying triggers wherein the above disadvan- Another object isy to provide a trigger operable over'an extremely wide variation in the supply voltage .and amplitude ofr keying pulses.

Another object .is to provide an inherently bijnarytrigger .circuit switchable 'to either stable Consequently of V.the trigger.

2 condition in response to a change in the value of the impedance Vin series with the plates or cathodes-of the trigger tubes.

AA further .object .is vto provide a trigger circuit operable from a single voltage supply wherein the cathode of the trigger tubes are connected through at least one grid controlled tube toits source of voltage supply.

A further vobject is to provide a 'novelltrfg'ger circuit` having the cathodes .of .its trigger tubes connected through a grid controlled tube tothe cathode .supply voltage and .its plate circuitconnected through agrid controlled tube tothe plate voltage supply,.said trigger circuit. being responsive to the simultaneous or successive application of keying pulses .from one or two sources. i

A still further object is to -providela trigger circuithaving the cathodes of the trigger vtubes connected to its voltage supply `through twoparallel connected impedances, the valueof .at least one impedance being changed-to sv'vitch` .the trigger from either. stable condition to theother.

A still further object is to provide an inherently binary trigger including a plurality of keying circuits-wherein eachkeying circuit is operably independent of and isolated from the other.

Generally, the invention includes anovel binary trigger-circuit using two grid controlled-tubesland having two stable conditions alternately assumed. Keying circuits are inter-.connectediwith the trigger tubes so that the trigger is .switched'in response to pulses from one keying circuit. -Each keying circuit vincludes at least one 'grid controlled tube connected `between either the :com-- monly joined cathodes of the .trigger tubes and the vsource of cathode voltage supply-or connected between the plate circuit of the trigger tubesiad the source of plate voltage supply; Switchingof the trigger from one .or two keying pulse sources isaccomplished by applying the pulses'toasingle keying circuit connected in series" with thecathodes of the trigger tubes. Also, switching of the triggers is obtained by applying the respective keying pulses to a keying .circuit `connected'in series with the cathodes .of the trigger tubes and to a keying circuit in series with the plate v.circuit The keying arrangements...de scribed herein are operable .in response.. to the negative going front of a peaked, Vsine wave or .rectangular pulses of low amplitude.. In order to simplify the descrip-tion, these keyingpulses are referred to hereinafter as merelyv keying pulses. The novel triggers permita'variationpf several hundred per cent `in the supply.-vo1'ta'g .e

3 and are operable at much higher keying speeds than those of the prior art.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, wh1ch disclose; by-way of example, the principle of the invention and the best mode, which has been contemplated of applying that principle.

In the drawings:

Fig. 1 is a circuit diagram of a trigger circuit employing a keying circuit in series with the cathodes of the trigger tubes.

Fig. 2 is a circuit diagram of a trigger circuit employing a keying circuit inthe platey and cathode circuits of the trigger tubes.

3 is a circuit diagram of a trigger circuit employing a keying circuit using a single multigrid tube to effect keying from two sources.

Fig. 4 is a circuit diagram of another embodiment utilizing principles illustrated by Fig. '1.

Fig. 5 is a circuit diagram showing a modification of the embodiment shown in Fig. 4.

Fig. 6 is a circuit diagram of another embodiment showing triode tubes connected in series with `the cathodesof the trigger tubes to form the keying circuit.

Fig. 7 is a circuit diagram showing a modification of the embodiment shown in Fig. 6 wherein .both the cathode and grid circuits of the trigger tubes are terminated in the keying circuit.

Referring more particularly to the drawings, each trigger circuit includes a 6SN'7 type tube A. Each tube A includes two triode sections, AI and A2 referred to herein astriodes AI and A2. While the `GSN'T type tube has two tubes in a single envelope it is understood that the triodes AI .and A2 may be ofthe type where only one triode is in an envelope. The two stable conditions of the triggers are referred to herein as on and oil The "on condition is assumed when the righthand triode'AZ is conductive and the left-hand triode AI isnon-conductive. The off" condition is assumedrwhen ,the right-hand triode A2 is non-conductive and the left-hand triode AI is conductive.

The dot at the left of the trigger tube A indicates that the triode AI isassumed to be initially conductive and that the trigger is ofi This is merely for the purpose' of facilitating the explanation throughout the several figures.

The arrangement and operation of the trigger circuits' will be described with reference to the values of applied voltage and the values' of resistances and capacitances employed therein.

These values are given solely for the purpose of clarifying the 'explanation and it is to be specifi'- cally understood that they may be varied considerably without departing from the principles of the invention.

Referring more particularly to Fig. 1 the trigger circuit includes the trigger tube A and a keying circuit including the BSN'? type tube B having triode tube sections BI and B2 referred to herein as triodes BI and B2. The cathodes of Vthe triodes AI and` A2 are connected together and through a potentiometer I to the commonly connected plates of the triodes BI and B2. The plate of the triode AI isconnected through a resistor Il of 10,000 ohms to a +250 volt line I2 and the plate of the triode A2 is connected through a resistor I3 of 10,000 ohms to the +250 volt line I2. The plate of the triode AI is connected through a lead I4 and through a resistor I of 100,000 ohms anda capacitor I'E- of 0.400005 microfarad, in parallel, to the control grid of the triode A2. The lower end of the resistor I5 is connected through a resistor II of 100,000 ohms to a zero volt line I8. Likewise, the plate of the triode A2 is connected through a lead I8 and through a resistor 20 of 100,000 ohms and a capacitor 2I of 0.00005 microfarad, in parallel, to the control grid of the triode AI. The lower end of the resistor 20 is connected through a resistor 22 of 100,000 ohms to the zero volt line I8. The cathodes of the triodes BI and B2 are connected directly to the zero volt line I8. Resistors 23 and 24, each of 10,000 ohms, are connected from the control grids of the triodes BI and B2 respectively to the Zero volt line I8. Keying terminals 25 and 2S are connected through capacitors 21 and 28 respectively, each of 0.00005 microfarad, to the control grids of the triodes BI and B2.

The control grids of the triodes BI and B2 `are normally at zero bias and both triodes are therefore highly conductive. Hence, a keying pulse applied to the control grid of either triode will reduce conduction through that triode.

The keying pulses, when applied to one of the triodes BI and B2, effect suiiicient reduction of current flow through that triode to initiate a switching of thetrigger from either stable condition to the other. Hence, the trigger may be keyed by either the successive or simultaneous application of keying pulses to the terminals 25 and 26.

`Since the keying pulses employed have a relatively low amplitude, such as for example 2 or 3 volts, positive pulses of corresponding amplitude are quenched and do not sufficiently effect the current flow through either triode BI or B2 to switch the trigger.

When a negative pulse is applied to one of the terminals 25 or 26 the current flow through the corresponding triode BI or B2 is decreased and the voltage at the cathodes of the triodes AI and A2 correspondingly increased. This increase of voltage at the cathodes is equivalent to impressing' a negative bias on the control grid of the triode AI since the trigger is ofi This increase of voltage causes a decreased voltage drop across the plate resistor I I. The resulting positive voltage at the plate of AI is transferred through lead I4 and the parallel connected resistor I5 and capacitor I6 to the control grid of triode A2 to render that triode conductive. As a result the voltage drop across plate resistor I3 is increased, the resulting negative voltage being transferred over the lead I9 and the parallel connected resistor 20 and capacitor 2| to the control grid of the triode AI to render it still less conductive. The increased positive voltage at the plate of triode AI is again transferred to the control grid of the triode A2 to render the latter still more conductive. This cumulative trigger action is continued until the triode A2 is rendered uniformly conductive and the triode AI is rendered non-conductive to switch the trigger on.

The next keying pulse applied to the terminals 25 and 26 or to either of them causes a similar increased voltage at the cathodes of the triodes AI and A2. VThis increased voltage results in an increased positive voltage at the plate of the triode A2 and a transfer thereof through the lead I 9 and the parallel connected resistor 20 and capacitor 2I to the control grid of the triode AI. 'Ihe resulting negative voltage at the plate of the triode AI is transferred over the lead Il and the parallel connected resistor I5 and capaci-1 acca-,caio

tor I6 tothe control-grid of the triode A2 Vtorender A2 still less conductive. The Vresulting positive yvoltage at the plate of the triode A2 is again transferred to the control grid of the triode AI vto render it still more conductive. This cumulative trigger action is continued until the triode AI is rendered uniformly conductive and the triode A2 is rendered non-conductive to switch the trigger off.

Itis seen that the small keying pulses applied to either terminal 25 or 26 cause a relatively large voltage change at the cathodes of the tube A because of the amplication provided 'by the tube B. Potentiometer I0 is providedto adjust the potential of ythe cathodes of the trigger ltube A so that when either of the triodes Al or A2 conducts its-grid bias is substantially zero. Obviously, the potentiometer I0 may be replaced by a fixed load if the keying pulses are of substantially constant amplitude.

Referring to Fig. 2 the voltage supply to operate the trigger circuit is supplied between a +400 volt line 30 and a zero volt line 3|. The values of resistors 32, 33 and 34 are 20,000 ohms,

200,000 ohms, and 200,000 ohms respectively, and "f `the values of resistors 35, 36 and 31 are 20,000 ohms, 200,000 ohms, and 200,000 ohms respectively. The capacitors 38 and 39 each have a value of 0.0001 microfarad.V I'he ,triode BI has its cathode connected to the commonly connected plate resistors 32 and 35 and its plate connected to the +400 volt line 30. The control grid of `triode Bl is connected through 'resistor 40 of 150,000 ohms to vthe line 30. The commonly connected cathodes of tube A are connected through the potentiometer I0 to the vplate of the triode B2 and the cathode of B2 is lconnected through Va potentiometer 4| to the .zero volt line 3|. It is seen that this circuit arrangement 'and the components employed are similar to those yemployed in Fig. 1 except for the differences noted above.

The triodes BI and B2 are normally highly conductive. A keying pulse applied to the terminal 26 decreases the conduction through the triode B2 and causes a switching of the trigger in the manner described in connection with Fig. `l.

A keying pulse applied to the'terminal 25 causes decreased conduction through the triode Bi and a corresponding increase in the voltage drop across it. As a result the voltage at the control grid of the conducting triode Al is decreased and causes an increased voltage to appear at its plate. This increased voltage is transferred to the rcontrol grid of the non-conducting triode A2 vto initiate conduction through it. The resulting decreased voltage at the plate of triode A2 is then transferred to the control grid of triode A'I to further decrease conduction through AI. This cumulative trigger action is continued until the triode Al is non-conductive and the triode A2 is uniformly conductive to switch .the trigger on The next keying pulse applied to the terminal 25 causes a similar decrease in the voltage at the control grid of the triode A2 and initiates the cumulative trigger action which finally switches the trigger oiff 'Ihe circuit of Fig. 2 retains all of the advantages of that of Fig. 1. An additional advantage of the circuit of Fig. 2 is that potentiometer 4I may be adjusted to operate the triode B2 as either an amplifier or a cathode follower in order that the potential of the cathodes of the trigger tube A will vary linearly with a change in the voltage between the lines I8 and I2. The adpositive, hence tube lC ,is highly conductive. keying 4pulse Vapplied ito :the terminal .25 .or 26 iustmentzoi'potentiometcr ,Il will lchaneefthe .bias on the1triod'e'B2 and therefore 'permit `keying iin response to. positive for vnegative fkeying, pulses without changing or adjusting the circuit arrangement associated iwith the .trigger tubeA.

Referring -to lFig. 23 the 'keying rcircuit includes :a =6AS6 pentode type tubeC. The k.plate of tube .Cris .connected :directly to .the commonly :connected-cathodes .of fthe'trigger tube A, but it understood :that ya ,plate load .may :be 'provided vfor lthe'purpose'sstated y'in connectionwith the potentiometer t0 `oi'- Fig. .1. The :screen grid of :the 'tube .1C is connectedwjto `the +250 vvolt line `i2 'through a resistor .42 .of 'such value Athat :1.00vo1ts is impressed' fon vthe screen grid. .A `by-pass icapacitor 543 lfis 'also lconnected to. .the screen grid and Vis of isuch value that the `bias voltage supplied through the resistor V42 to the screen grid `will be 'held 'at fa 'substantially Vconstant value. The control' 'grid lof 'the 'tube C is connected through ythe capacitor 21 tothe. keying `terminal 25 'and lthe suppressor vgrid is connected through uthe capacitor Y28 'to Athe keying terminal 26. It 4is obvious from "the :circuit arrangement that the bias on the `control' Agrid and suppressor grid is .zero and that the 'bias :on the screen vgrid is A will `place Ka negative'bias on the .corresponding grid of fthe .tube C and Will therefore .decrease vthe conduction through the tube C and place an Aincreased"*voltage on the cathodes .of the .triodes A1 and-A2. vThis increasedvoltage will cause a switching ofthe trigger vas .described .in .connection with Fig. 1. Since the application cfa keyingpulse to either the control or suppressorgrid of vtube V.C results lin a switching of the trigger it Vis .clear :that the Vtrigger vis responsive `to rthe simultaneous and successive `application of keying pulses l'to `terminals '25 and 26. This circuit illustrates one-way -to switch a trigger from `two sources with a keying circuit `including only one tube while retaining 'the .advantages of the circuits of Figs. 1 Iand 2.'

Referring to` Fig. r4 Ythere is .shownsubstantially the circuit .arrangement of ',Fig. 1. .'In this embodiment only triode B2 is :utilized and 'its cathode :is vconnected through the ,potentiometer 41 'to Vthe line :IB-'and capacitors 64 and 45 each having a vvalue of '0.'0000561microfarad- This circuit arrangementillustrates one way of .switching `a trigger, in `accordance with the 'principles of the invention, in'response to'fpulses from a single keyingsource. Y

Referring to Fig. 5 there is shown a circuit 'arrangement substantially as `in Fig. 4 except that lthe plate ofthe triode BI is connected directly tothe cathodes of thetrigger tube A and its cathode Ais connected directly to vthe zero volt line I8.

'In addition, germanium crystal rectiers G are connected between the control grid of triode Bl and the line I 8. These rectiflers are provided to insure that positive 4pulses irrespective of their lamplitude will be ineffective to switch the trigger circuit. These rectiliers eliminate any possibility of a switching of the trigger in response to positive -keying pulses of high amplitude because of the .low impedance path provided by the rectiers `.between the .control .grid of the triode Bl and the ,line IB.

Referring to Fig. 6 there is `showna modiiication of .the .circuit arrangement .of Fig. 1. The .plate .of `the triode'B2 is connected .directly to the cathodes of the trigger tube A. 'I'he cathode of the triode B2 is connected to the plate of the 4atcarsso 'l triode Bl and the control grid of B2 is connected through the resistor 24 to-'the cathode of'B2. 'Ihe cathode of triode Bl 'is connected directly to the zero voltline i8. I

Triodes Bl and B2 are normally highly conductive and Since they are connected in-series, a change in the conduction through one -triode causes a similar change in the conduction through the other triode. Hence theapplication of 'keying pulses to either or both of the terminals 25 and 26 causes a decrease in the conduction through the triodes BI and B2 and a-c'orresponding-increase in the voltage at the cathodes of the trigger tube A causes a switching of the 'trigger in the manner described in connection with Fig. 1.

The use of the triodes BI and B2- connectedin series is particularly advantageous'over their use in parallel as illustrated in Fig. l. lWhen'connected in parallel one triode, due to its conduction when keying pulses are applieds'uccessively to the triode, tends to prevent a change in voltage at the cathodes of the trigger tube A and thereby tends to decrease the effect 'offithe keyedtriode on the voltage at those cathodes.` But when' the triodes are connected in series the voltage change caused by either triode is transferredto the cathodes of the tube A without Lany decreasedeffectfbeing caused by the other triode. This is because the conduction through either triode BI or B2 in Fig. 6 controls conduction through theother.

Referring to Fig; 7 there is shown a circuit arrangement similar tothat of Fig. 6 except that the lower end ofthe resistors V22 and llterminate at the commonly-connectedplate of triode BI and cathode of triode B2. e

The trigger circuitsy of Fig. *1' throughv Fig. 7 inclusive, in addition to the advantages -pointed out above, ndparticular 'utility'fwhere a trigger is required having a very fast period of response. The triggers of the in'ventionA will switch from either stable condition to the other in response to keying pulses having a separation in time which does not exceed or is even lessthan the time required for the trigger to switch completely from eitherI stable condition to the other. The ltrigger characteristic which permits a Subsequent switching of the trigger before it has switched c ompletely to a stable condition in response to the last keying pulse is attributed to the avoidance of 'feedback effects through Vthe novelkeying-arrangement.` y l While there have beenshown and described and pointed out the fundamentalnovel.ieaturesof the invention as applied to preferredlembodiments, it will be understood that.variousomis sions and substitutions and changes in the form and details of the triggers illustrated andfin their operation may be made by those skilled in the art, without departing from the spirit of `the invention. It is the intention, therefore, to be limited only as indicated by the scope ofthe following claims. Y i

What is claimed is: 1

l. A trigger circuit including two Vcross-connected triode vacuum tubes and having two stable conditions alternately assumed during each of which a different one of said tubes is conductive, the cathodes of said tubes being commonly connected together and the plates of said tubes being connected together throughresistors; a high and a low voltage line; rst and secondI sources of keying pulses; rst and second grid controlled keying tubes normallyconductive, said rst key- Ying tube having its cathode connected to said resistors and its plate connected to said high voltage line; a rst potentiometer connected between the cathodes of said vacuum tubes and the plate of said second keying tube; a second potentiometer connected between the cathode of said second keying tube and said low voltage line, said first and second potentiometers permitting operation of said second keying tube as an amplier or a cathode follower; means for applying keying pulses from said rst source to the control grid of said first keying tube to decrease the voltage at the control grid of the conducting vacuum tube to initiate a switching of the trigger to the other stable condition and means for applying keying pulses from said second source to the control grid of said vacuum tubes to initiate a switching of the triggers to the other stable condition.

2. A trigger circuit including two cross-connected grid controlled vacuum tubes and having two stable conditions alternately assumed during each oi which a diiierent one of said tubes is conductive and non-conductive respectively; a conductive connection only between the cathodes of said tubes; a high and a low yvoltage line; a plate resistor connected between the respective plates of said tubes and said high voltage line; a source of pulses for effecting a switching of the trigger from either stable condition to the other; only a variable impedance, normally at a low value, connected between said conductive connection and said low voltage line; means for applying pulses from said source to said variable impedance to automatically adjust said impedance toa higher value to increase the voltage at the cathode of each of said vacuum tubes to cause a switching oi the trigger from either stable condition to the other; a potentiometer connected between said variable impedance and said conductive connection to adjust the voltage change at the cathodes of said vacuum tubes when the impedance is adjusted from said. low value to said higher value.

3. The'trigger circuit set forth in claim` 2 wherein a potentiometer is connected between said variable impedance and said low voltage line to provide for controllable adjustment of the change in the value of said impedance in response to said pulses.

ARTHUR H. DICKINSON.

REFERENCES CITED Thc'following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,106,342 Doba J an. 25, 1938 2,404,047 Flory et al July 16, 1946 2,405,843 Moe Aug. 13, 1946 FOREIGN PATENTS Number Country Date 584,740 Great Britain Jan. 22, 1947 OTHER REFERENCES Physical Review, vol. 57, 1940, New Vacuum Tube Scaling Circuits of Arbitrary Integral or Fractional Scaling Ratio, by Lifschutz, pages 243 and 244.

Review of Scientific Instruments, vol. 14, January 1943, Simplified Scaling Circuit, by De- Vault, page 23. 

